1. Technical Field
The present invention relates to a sample manufacturing apparatus and, more specifically, to an apparatus for making test pieces for slice observation from a wafer with a transmission electron microscope (hereafter referred to as TEM) or a scanning electron microscope (hereafter referred to as SEM) utilizing ultra-fine processing using a focused ion beam (hereafter referred to as FIB).
2. Related Art
An FIB device is known as a device for manufacturing a test piece such a TEM sample or an SEM sample from a wafer, being an original sample. A schematic drawing of an FIB device of the related art is shown in FIG. 10. The main components of this FIB device are an ion source 100, an ion optical system 101, a secondary charged particle detector 102, a gas gun 103, a sample holder 104 and a sample stage 105.
The ion source 100 is a liquid metal ion source exemplified by, for example, gallium (Ga). The ion optical system 101 is for focusing an ion beam from the ion source 100 and is comprised of a condenser lens (electrostatic lens) a beam blanker, a movable aperture, an 8-pole stigmeter, an objective lens (electrostatic lens) and a scanning electrode. The secondary charged particle detector 102 detects secondary charged particles generated when an ion beam 100a is scanned on the sample 106, and a scanning ion microscope (hereafter referred to simply as SIM) function is provided by carrying out image processing based on the detection results. The sample stage 105 is a stage capable of movement on 5 axes of control. With 5 axes of control it is possible to achieve 3-dimensional movement in the XYZ directions, rotation around an axis orthogonal to the XY plane, and tilt control. The sample holder 104 is for fixing the sample 106, and is mounted on a movable platform called a base (not shown in the drawings) and conveyed on to the sample stage 105. The gas gun 103 sprays gas for forming a deposition film as a protective film onto the surface of the sample 106.
There are basically the following two methods in sample manufacture using the above described FIB device. One is a method of fixing a small sample that has been subjected to preliminary processing by cutting away part of a wafer using a dicing saw on a holding member, fixing this to a sample holder 104 as a sample 106, and processing using an ion beam 100a. Another is a so-called pick-up method (or lift-out method) where the wafer itself is fixed to the sample holder 104 as the sample 106, a specific site on the sample holder 104 is directly processed by the ion beam 100a, and the test piece taken out. The latter method can manufacture a test piece (TEM sample or SEM sample) without dividing the original sample, which means that compared to the former method which splits the wafer to make a small piece, there are the merits that it is advantageous with respect to cost, and the sample manufacturing time is short.
FIG. 11 schematically shows a sequence of manufacturing processes for a TEM sample using the pick-up method, in which the FIB device shown in FIG. 10 is used. The manufacturing processes for a TEM sample will be described in the following with reference to FIG. 10 and FIG. 11.
First, a wafer, being the sample 106, is fixed onto the sample stage 105, and based on previously provided position information for a specific site rough alignment is carried out so that the ion beam 100a is irradiated close to that specific site. Next, the vicinity of a fault site is scanned with the ion beam 100a, and the position of a fault site is specified while looking at an SIM image obtained by this scanning (position output). After position output, deposition gas is sprayed onto the surface of the wafer using the gas gun 103, and a deposition film (protective film) for the surface of the wafer is formed by scanning a specified range containing the specific site with the ion beam 100a. Formation of this deposition film is generally called ion assist deposition (or ion beam CVD (Chemical Vapor Deposition), and it is possible to selectively form a deposition film on sections irradiated by the ion beam 100a. 
Next, as shown in FIG. 11A, the ion beam 100a is irradiated to the vicinity of the specific site of the wafer surface to perform general processing, and the ion beam 100a is also irradiated to that processed section to perform finishing processing. With this processing, the ion beam 100a is irradiated from a normal direction with respect to the surface of the wafer, which means that the region irradiated by the ion beam 100a is gradually removed from the wafer surface, to obtain the slice 107a as shown in FIG. 11B. The extent to which the thickness of the slice 107a section looking from above is made thinner is different depending on the material of the sample and the acceleration voltage of a TEM used. For example, in the case of lattice image observation of an Si type semiconductor sample with a 200 kV acceleration voltage TEM, this must be 0.1 μm or less. Also, in the case of carrying out 3D analysis with tomography using a TEM, the sample thickness is finished to about 0.5 μm.
After formation of the slice 107a, the angle of incidence of the ion beam 100a to the wafer is adjusted by controlling the tilt angle of the sample stage 105, and a notch 107b as shown in FIG. 11B (the section shown by a dotted line in FIG. 11B) is formed around the section where the slice 107a is formed by processing using the ion beam 100a. A part at an upper surface side remains that is not notched, and a section taken out along the notch 107b is the TEM sample 107.
A manipulator, not shown, is used in taking out the TEM sample 107. A tip of a probe 108, made of a glass material, is brought close to a lateral slice 107a of the TEM sample 107. If the tip of the probe 108 is brought sufficiently close to the slice 107a, then as shown in FIG. 11C, the TEM sample 107 is attracted to the probe 108 due to static electricity. Then, with the TEM sample 107 still stuck to the tip, the probe 108 is mode onto a fixing table (not shown) that has been separately prepared, and the TEM sample 107 stuck to the tip is fixed to a specified part of the fixing table. In fixing the TEM sample 107 to the fixing table at this time, it is possible to utilize deposition processing or static electricity. Depending on the situation, it may also be possible to perform finishing processing for the TEM sample 107 fixed to the fixing table using the ion beam 100a. 
When carrying out TEM observation, the fixing table to which the above described TEM sample 107 is fixed is taken out from the FIB device, and attached to a separately prepared TEM sample holder. This TEM sample holder is then fitted into an entry stage of a TEM device that is separate from the FIB device, and the slice 107a of the TEM sample 107 is observed.
With manufacture of the TEM sample using the FIB device described above, outside the FIB device a fixing table to which the TEM sample 107 is fixed is attached to the TEM sample holder, and after TEM observation in the event that the TEM sample is processed again, it is necessary to remove the fixing table to which the TEM sample is fixed is from the TEM sample holder, fix the sample holder again, and convey onto the sample stage inside the FIB device. This is extremely bad from an operating point of view.
Recently, methods have been proposed where manufacture of a test piece, such as a TEM sample, and fixing to a sample holder for observation of the manufactured test piece (such as a TEM sample holder) can be carried out sequentially inside the FIB device. As one example, there is a sample manufacturing device as disclosed in Japanese Patent laid-open No. 2000-155081. FIG. 12 shows the schematic structure of this sample manufacturing device.
The sample manufacturing device shown in FIG. 12 has an FIB irradiation optical system 202, a secondary electron detector 203, a deposition gas source 204, a sample movement mechanism 206, a test piece probe movement mechanism 209 and an observation sample holder movement mechanism 211 provided in a sample processing chamber 201 that has been evacuated using a vacuum pump 200.
The sample movement mechanism 206 has an original sample 5 mounted thereon, and imparts relative displacement for an FIB original sample 5 irradiated from the FIB irradiation optical system 202 with respect to the original sample 5. The test piece probe movement mechanism 209 has a test piece probe holder 208 attached thereto, and enables three dimensional movement of the test piece probe holder 208. An observation sample holder 210 is attached to the observation sample holder movement mechanism 211, and three dimensional movement of the attached observation sample holder 210 is enabled. These movement mechanisms enable delivery of a test piece probe 207 between the test piece probe holder 208 and the observation sample holder 210.
With the above described sample manufacturing device, a specific site of a wafer, being the original sample 5, is processed by an FIB from the FIB irradiation optical system 202 to form a cantilever shaped test piece, a specific site of the test piece probe 207 held on the test piece probe holder 208 is brought into contact with part of this cantilever shaped test piece, and fixed by deposition processing. Also, part of the cantilever shape is processed by the FIB from the FIB irradiation optical system 202 to be cut away, and a test piece is separated from the original sample 5. The test piece probe 207 to which the separated test piece is fixed is then delivered from the test piece probe holder 208 to the observation sample holder 210.
As well as the above, there is an FIB sample manufacturing device provided with a side entry stage to which it is possible to attach a TEM sample holder, as disclosed in Japanese Patent Laid-open No. 2002-62226. FIG. 13 shows the schematic structure of this FIB manufacturing device.
The FIB manufacturing device shown in FIG. 13 has an ion beam irradiation system 301, a manipulator 305, a TEM sample stage 306, being a side entry stage, and a wafer sample stage 304, to which a wafer 303 is fixed, provided in an FIB sample chamber 302 that has been evacuated by an evacuation pump, not shown.
The vicinity of the center of the FIB sample chamber 302 constitutes an FIB processing position, and the ion beam irradiation system 301 is arranged so that the optical axis passes through the vicinity of the center of the FIB sample chamber 302. The TEM sample stage 306 is capable of movement in the horizontal direction (the direction of the arrow B), and it is possible to insert a TEM sample holder that is shared between this FIB sample manufacturing device and a separately prepared TEM device. The wafer sample stage 304 is provided with a movement mechanism for moving up an down in the vertical direction, that is, the direction of arrow A (Z direction) along the optical axis of the ion beam irradiation system 301 (central axis of the lens barrel).
With the above described FIB sample manufacturing device, first of all, after the TEM sample stage 306 has been made to retreat to a position that is sufficiently apart from the FIB processing position, the wafer sample stage 304 with the wafer 303 mounted thereon is moved to the FIB processing position. Then, a specific site of the wafer 303 is processed by an ion beam from the ion beam irradiation system 301, and part of that processed section is taken out and held by the manipulator 305 as a TEM test piece.
Next, as shown in FIG. 14, after the wafer sample stage 304 has been made to retreat to a position that is sufficiently apart from the FIB processing position, the TEM sample stage 306 to which a TEM sample holder 311 is attached is moved to the FIB processing position, and the previously held TEM test piece is fixed to a specified part of the TEM sample holder 311 using the manipulator 305. Then, an ion beam from the ion beam irradiation system 301 is irradiated to the test piece fixed to the TEM sample holder 311 to perform finishing processing.
According to the above described FIB sample manufacturing device, it is possible to carry out processing to manufacture a TEM test piece from a wafer and processing to fix the manufactured test piece to a TEM sample holder inside the FIB sample chamber. Further, when processing the TEM test piece again after TEM observation, it is possible to simply attach the TEM sample holder to the TEM sample stage of the FIB sample manufacturing device again.
As described above, with sample manufacture using the FIB device shown in FIG. 10, there is a problem that operability is bad.
In the sample manufacturing device disclosed in Japanese Patent Laid-open No. 2000-155081, since manufacture of a test piece and fixing of the manufactured test piece to a test piece observation sample holder within the FIB device is carried out sequentially, it is possible to solve the above described problem with respect to operability, However, in this case there is the following problem.
At the FIB device, since with the above described stricture it is not possible to make the sample processing chamber 203 very large, the FIB irradiation optical system 202, gas source 204, detector 203, sample movement mechanism 206, observation sample holder 210 and the test piece probe holder 208 are arranged close together in the limited space of the sample chamber 263. With the structure shown in FIG. 12, the observation sample holder 210 and the test piece probe holder 208 both have tips arranged in the horizontal direction so as to cross at the FIB processing position, and with this type of arrangement there is sometimes interference between each of the holders and the sample movement mechanism 206 arranged below the FIB processing position.
By causing the sample movement mechanism 206 to retreat sufficiently from the FIB processing position, it is possible to avoid interference with the holders, but in limited space it is difficult to ensure a space for retreating, and it is not practical. Also, if, for argument's sake, it was possible to ensure such a space, the sample processing chamber 203 would be enlarged by the extent of that space, and the device would be made larger. If the sample processing chamber 203 is made larger, it will become impossible to sufficiently evacuate the inside of the chamber. Also, because the stroke of the sample movement mechanism 206 will be made longer, there is a danger of FIB processing precision being lowered due to vibration.
In the FIB sample manufacturing device disclosed in Japanese patent laid-open No. 2002-62226 it is also possible to solve the above described issue regarding operability, but there is the following type of problem.
As shown in FIG. 13, the wafer sample stage 104 and the TEM sample stage 106 move respectively in the vertical direction and the horizontal direction so as not to interfere with each other. It is difficult to ensure this type of movement space in the limited space of the sample chamber, and is not really possible. Also, the device (sample chamber) is enlarged by the extent of any movement space provided, making the device bulky. Further, if the sample chamber is made larger, it will become impossible to sufficiently evacuate the inside of the sample chamber.
Also, in order to move the wafer sample holder 104 to a position where it does not interfere with the TEM sample stage 106, a certain stroke length is required. If the stroke length of the wafer sample stage 104 is made long, the FIB processing precision will be lowered due to vibration of the wafer sample stage 104.
The object of the present invention is to solve each of the above described problems in the conventional art, and to provide a compact sample manufacturing device in which a sample stage and an observation sample holder (side entry stage) do not interfere.